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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 775 records · Page 43
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

Anticipated uncertainty budgets of PRARETIME and T2L2 techniques as applied to ExTRAS

The Experiment on Timing Ranging and Atmospheric Soundings, ExTRAS, was conceived jointly by the European Space Agency, ESA, and the Russian Space Agency, RSA. It is also designated the 'Hydrogen-maser in Space/Meteor-3M project'. The launch of the satellite is scheduled for early 1997. The package, to be flown on board a Russian meteorological satellite includes ultra-stable frequency and time sources, namely two active and auto-tuned hydrogen masers. Communication between the on-board hydrogen masers and the ground station clocks is effected by means of a microwave link using the modified version for time transfer of the Precise Range And Range-rate Equipment, PRARETIME, technique, and an optical link which uses the Time Transfer by Laser Link, T2L2, method. Both the PRARETIME and T2L2 techniques operate in a two-directional mode, which makes it possible to carry out accurate transmissions without precise knowledge of the satellite and station positions. Due to the exceptional quality of the on-board clocks and to the high performance of the communication techniques with the satellite, satellite clock monitoring and ground clocks synchronization are anticipated to be performed with uncertainties below 0.5 ns (1 sigma). Uncertainty budgets and related comments are presented.

Thomas, Claudine↗
NASA NTRSDate not supplied

Multi-Impulse to Time Optimal Finite Burn Trajectory Conversion

A novel algorithm is presented that provides an improvement over a traditional parameter optimization method when solving time-optimal, finite-burn pseudo-rendezvous spacecraft trajectory problems. A hybrid optimization procedure is described that converts a set of multiple-impulses, representing high- or low-thrust maneuvers, to an exact time-optimal finite-burn trajectory for a thrust limited, constant exhaust velocity spacecraft. The Hybrid Method applies a control law derived from the Euler-Lagrange system of equations within the classical Indirect Method to a modern Direct Method. An iterative adjoint-control transformation and an evolving constraint vector are introduced to solve the optimal control two-point boundary value problem. This method requires no prior knowledge of the solution, which adds simplicity to the trajectory design process and aids automation. Examples are shown for low-thrust apogee raise maneuvers, non-coplanar Earth orbit transfers, and a modified Deep Space 1 low-thrust trajectory. A numerically significant improvement to objective cost is shown across all application problems compared to a traditional solution method, as well as a significant improvement to convergence speed for a select class of problems.

Joshua A Fogel↗
NASA NTRSDate not supplied

NASA's Innovative Entry Systems and TPS Technologies Enabling Commercial Space Missions

For over six decades, the NASA Ames Entry Systems and Technology Division has been a cornerstone of U.S. space exploration, delivering critical atmospheric entry solutions since Project Mercury and now increasingly supporting the commercial space sector. The Division provides reliable entry system solutions through a unique blend of expertise, national facilities, and systems integration knowledge, a combination that is difficult to replicate outside a dedicated government entity. Consistently successful, the TS Division remains central to NASA’s exploration objectives and significantly contributes to the transfer of technology to the commercial space sector, supporting more than ten commercial space companies and supplying flight heatshields to three of them in the past five years. Its strengths in Thermal Protection System (TPS) materials, aerothermodynamics, ground test facilities, and Entry, Descent, and Landing (EDL) systems engineering drive rapid development and sustained U.S. competitiveness in space. The Division's expertise in reusable and ablative thermal protection systems, as well as mechanically deployable entry systems primarily developed for NASA missions, now benefits commercial space missions. This presentation will highlight the vision and needs of these commercial space companies, how NASA-invented technologies meet mission requirements, and how these technologies enable and distinguish their efforts.

Ethiraj Venkatapathy↗
DOE OSTI2023

Machine learning-based surrogate models and transfer learning for derivative free optimization of HT-PEM fuel cells

Widespread adoption of high-temperature polymer electrolyte membrane electrochemical systems, such as fuel cells (HT-PEMFCs), requires models and computational tools for accurate optimization and guiding new materials for enhancing performance and durability. In this contribution, knowledge-based modelling and data-driven modelling are combined using Few-Shot Learning and implementing an Automated Machine Learning framework for the generation of Machine Learning-based surrogate models. Applicability of the resulting model for derivative-free optimization is demonstrated. Additionally, a way of considering extrapolation in the optimization task is presented. Results show that although extrapolation is needed to achieve better solutions during optimization, it can be monitored and managed. As a result, tuning the electrode ionomer binder's properties, such as ionic conductivity, in the fuel cell represents a promising pathway for improving HT-PEMFC performance.

08 HYDROGEN↗
DOE OSTI2016

Nuclear Data Sheets for A = 41

Available information pertaining to the nuclear structure of all nuclei with mass numbers A=41 ranging from Al (Z=13) to Ti (Z=22) are presented. The experimental reaction and decay data are evaluated and any inconsistencies or discrepancies are noted. The adopted values for various level properties (such as the spin, parity and and halflife) and gamma properties (energy, intensity and multipole character) are given. Since the prior evaluation several new measurements have expanded our knowledge of A=41 nuclides. The half-life of the ground state of {sup 41}Si has been determined and a single excited state identified. Excited levels in {sup 41}P have been observed for the first time. In {sup 41}Cl, seven new excited states have been identified in deep inelastic and heavy ion transfer reactions. Half-lifes for four states in {sup 41}Ar have been updated and additional levels with gammas have been included from a new measurement using the multiple ion transfer reaction. In {sup 41}Ca via charge-exchange reaction measurements, several new excited states were observed. A number of new resonances in {sup 41}K have been identified via the (p,γ) reaction. There remains a significant discrepancy in the half-life of the first excited state (980 keV) in {sup 41}K, with measurements differing by more than an order of magnitude. Transfer reactions suggest that this M1 transition should be l-forbidden, however, several measurements yield a lifetime which suggests a sizable M1 strength. Further measurements to resolve the current conflicts would be beneficial.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS2016

Expansion of Tabulated Scattering Matrices in Generalized Spherical Functions

An efficient way to solve the vector radiative transfer equation for plane-parallel turbid media is to Fourier-decompose it in azimuth. This methodology is typically based on the analytical computation of the Fourier components of the phase matrix and is predicated on the knowledge of the coefficients appearing in the expansion of the normalized scattering matrix in generalized spherical functions. Quite often the expansion coefficients have to be determined from tabulated values of the scattering matrix obtained from measurements or calculated by solving the Maxwell equations. In such cases one needs an efficient and accurate computer procedure converting a tabulated scattering matrix into the corresponding set of expansion coefficients. This short communication summarizes the theoretical basis of this procedure and serves as the user guide to a simple public-domain FORTRAN program.

scattering matrix↗
DOE OSTI2016

SU-G-JeP2-11: Polymer Gels as 3D QA Devices in Magnetic Resonance-Guided Radiation Therapy

Purpose: To demonstrate the potential of polymer gels to serve as 3D QA devices in MR-guided radiotherapy. Methods: Custom-designed polymer gel dosimeters (MGS Research, Madison, CT) were centered on the penumbras of a radiation field, parallel to the magnetic field lines inside a 1.5 T MR scanner integrated with a 7 MV linac (MR-Linac). 15 Gy were delivered perpendicular to the magnetic field. Coronal MR images were acquired with a 2D balanced-Fast Field Echo (b-FFE) sequence in real-time during irradiation and with a 2D spin echo sequence at different times after irradiation. Signal intensities (SI) were measured inside and outside the radiation field on b-FFE images obtained during irradiation. Spin-spin relaxation rate (R2) maps were calculated from images after irradiation and penumbra widths were calculated from these maps. Results: A difference in SI between areas of the dosimeter inside and outside of the radiation field could be measured immediately after the beam was turned on. The difference in SI increased throughout the duration of the exposure. R2 values from immediately after irradiation were 83% of those measured 24h post-irradiation. At 1h after irradiation, the R2 values were 87% of those at 24h indicating that polymerization of the gel was still ongoing. At 24h postirradiation the width of the 80/20 penumbra on the left field edge measured 6.5 mm and on the right 5.6 mm. Conclusion: The MR-Linac allows for MR imaging during treatment and measurements of 3D dose distributions with steep dose gradients without having to transfer dosimeters for read-out. The results showed promise for polymer gels as relative 3D QA devices to verify radiation treatment plans delivered by an MR-Linac. To our knowledge, this was the first time that polymer gels were used for real-time image acquisition. Further investigations into the application of polymer gel dosimetry on MR-Linac are ongoing.

60 APPLIED LIFE SCIENCES↗
NASA NTRS1976

Stability of laser heated flows

A local stability analysis is utilized to determine the stability of disturbances generated at each point along a nozzle of variable area ratio for a one-dimensional flow heated by laser radiation entering from the upstream direction. The governing equations for the quasi-one-dimensional flow without viscous dissipation, diffusion, and thermal conduction but including radiative heat transfer are given. The governing equations are combined to yield a relationship which governs the Mach number variation through the nozzle. The complete steady-state solution can be calculated from knowledge of the Mach number profile, the inlet conditions, and the laser power. The local stability analysis permits obtaining contour (or contours) of neutral stability. Solutions have been obtained for various nozzle configurations, but only one set of example calculations is presented. The results obtained indicate that the analysis serves as an important indicator as to where potential absorption wave phenomena may be initiated.

Wu, P. K. S.↗
NASA NTRS2009

Observation and Interpretation of Energetic Neutral Hydrogen Atoms from the December 5, 2006 Solar Event

We report the first observations of energetic neutral atoms (ENAs) from a solar flare/coronal mass ejection event. The observations were made during the December 5, 2006 X9 solar flare, located at E79, by the Low Energy Telescopes (LETs) on the STEREO A and B spacecraft. Within 1-2 hours of the flare onset, both LETs observed a sudden burst of 1.6 to 15 MeV protons arriving hours before the onset of the main solar energetic particle (SEP) event at Earth. More than 70% of these particles arrived from a longitude within +-10 degrees of the Sun. The derived emission profile at the Sun lasted for more than an hour and had a profile remarkably similar to the GOES soft X-ray profile. The observed arrival directions and energy spectrum argue strongly that the particle events <5 MeV were due to energetic neutral hydrogen atoms that were stripped of their electrons upon entering the LET sensor. To our knowledge, this is the first reported observation of ENA emission from a solar flare/coronal mass ejection. We discuss possible origins for the production of ENAs in solar events, including charge-transfer reactions involving both flare and shock-accelerated protons. Assuming isotropic emission, we find that ~2 x 10E28 ENAs escaped from the Sun in the upper hemisphere. Based on the 2.2 MeV gamma-ray emission observed by RHESSI in this event, and using measured and theoretical cross sections, we estimate that ~3 x 10E31 ENAs with 1.8 - 5 MeV could be produced by protons accelerated in the flare. CME-driven shock acceleration is also a possible ENA source, but unfortunately there were no CME observations available from this event. Taking into account ENA losses, we conclude that the observed ENAs were most likely produced in the high corona at heliocentric distances 1.6 solar radii.

Mewaldt, R. A.↗
DOE OSTI2016

Observation of the spectrally invariant properties of clouds in cloudy-to-clear transition zones during the MAGIC field campaign

We use the spectrally invariant method to study the variability of cloud optical thickness τ and droplet effective radius reff in transition zones (between the cloudy and clear sky columns) observed from Solar Spectral Flux Radiometer (SSFR) and Shortwave Array Spectroradiometer-Zenith (SASZe) during the Marine ARM GPCI Investigation of Clouds (MAGIC) field campaign. The measurements from the SSFR and the SASZe are different, however inter-instrument differences of self-normalized measurements (divided by their own spectra at a fixed time) are small. The spectrally invariant method approximates the spectra in the cloud transition zone as a linear combination of definitely clear and cloudy spectra, where the coefficients, slope and intercept, character-ize the spectrally invariant properties of the transition zone. Simulation results from the SBDART (Santa Barbara DISORT Atmospheric Radiative Transfer) model demonstrate that (1) the slope of the visible band is positively correlated with the cloud optical thickness τ while the intercept of the near-infrared band has high negative cor-relation with the cloud drop effective radius reff even without the exact knowledge of τ; (2) the above relations hold for all Solar Zenith Angle (SZA) and for cloud-contaminated skies. In observations using redundant measure-ments from SSFR and SASZe, we find that during cloudy-to-clear transitions, (a) the slopes of the visible band de-crease, and (b) the intercepts of the near-infrared band remain almost constant near cloud edges. The findings in simulations and observations suggest that, while the optical thickness decreases during the cloudy-to-clear transition, the cloud drop effective radius does not change when cloud edges are approached. These results sup-port the hypothesis that inhomogeneous mixing dominates near cloud edges in the studied cases.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1996

Technology Transfer External Metrics, Research, Success Stories, and Participation on Evaluation Team for the Reusable Launch Vehicle (RLV)

This research report is divided into four sections. The first section is related to participation on the team that evaluated the proposals for the X-33 project and the Reusable Launch Vehicle (RLV) during mid-May; prior to beginning the 1996 Summer Faculty Fellowship. The second section discusses the various meetings attended related to the technology evaluation process. The third section is related to various research and evaluation activities engaged in by this researcher. The final section discusses several success stories this researcher aided in preparing. Despite the fact that this researcher is not an engineer or science faculty, invaluable knowledge and experience have been gained at MSFC. Although related to the previous summer's research, the research has been new, varied, and challenging. This researcher was fortunate to have had maximum interaction with NASA colleague, David Cockrell. It would be a privilege and honor to continue a relationship with the Technology Transfer Office. In addition, we will attempt to aid in the establishment of a continuous formalized relationship between MSFC and Jacksonville State University. Dr. David Watts, Vice President for Academic Affairs, J.S.U., is interested in having the Technology Division cooperating with MSFC in sharing information and working tech transfer inquiries. The principal benefits gained by this researcher include the opportunity to conduct research in a non-academic, real world environment. In addition, the opportunity to be involved in aiding with the decision process for the choice of the next generation of space transportation system was a once in a lifetime experience. This researcher has gained enhanced respect and understanding of MSFC/NASA staff and facilities.

Trivoli, George W.↗
DOE OSTI2022

Chemical Challenges that the Peroxide Dianion Presents to Rechargeable Lithium–Air Batteries

Understanding the fundamental redox reactions and processes that occur in lithium–air and, more generally, metal–air batteries is important to the progress of this promising energy-storage technology. Knowledge of the chemistry of the peroxide dianion, O 2 2– , is especially crucial, as the dianion is at the nexus of the charge/discharge cycle of lithium–air batteries. The intrinsic electron transfer properties and redox chemistry of peroxide dianion are poorly defined because it is difficult to isolate the dianion free of protons and metal ions. We review the results of (i) the electron transfer kinetics and (ii) the redox reaction chemistry of isolated peroxide dianion encapsulated within the cavity of a hexacarboxamide cryptand. With regard to the former, electron transfer kinetics measurements provide fundamental Marcus parameters that will be useful for models that seek to disentangle the precise contributions of Li + ion-coupled electron transfer, electron transfer across the Li 2 O 2 solid particle interface, and charge hopping among Li 2 O 2 particles. With regard to the latter, an underappreciated chemistry of peroxide dianion with CO 2 produces peroxymonocarbonate (OOCO 2 2– ) and peroxydicarbonate (O 2 COOCO 2 2– ). An autocatalytic cycle will lead to oxidative degradation of traditional organic electrolytes and other vulnerable cell components employed in lithium–air batteries. Furthermore, this peroxycarbonate-derived chemistry, in addition to more commonly recognized solution-based oxidation chemistry, will need to be mitigated to realize the long-term cyclability of rechargeable lithium–air batteries.

25 ENERGY STORAGE↗
DOE OSTI2015

Tetrafluoroethane (R134a) hydrate formation within variable volume reactor accompanied by evaporation and condensation

Vast size hydrate formation reactors with fast conversion rate are required for the economic implementation of seawater desalination utilizing gas hydrate technology. The commercial target production rate is order of thousand tons of potable water per day per train. Various heat and mass transfer enhancement schemes including agitation, spraying, and bubbling have been examined to maximize the production capacities in scaled up design of hydrate formation reactors. The present experimental study focused on acquiring basic knowledge needed to design variable volume reactors to produce tetrafluoroethane hydrate slurry. Test vessel was composed of main cavity with fixed volume of 140 ml and auxiliary cavity with variable volume of 0 ∼ 64 ml. Temperatures at multiple locations within vessel and pressure were monitored while visual access was made through front window. Alternating evaporation and condensation induced by cyclic volume change provided agitation due to density differences among water and vapor, liquid and hydrate R134a as well as extended interface area, which improved hydrate formation kinetics coupled with latent heat release and absorption. Influences of coolant temperature, piston stroke/speed, and volume change period on hydrate formation kinetics were investigated. Suggestions of reactor design improvement for future experimental study are also made.

42 ENGINEERING↗
DOE OSTI2017

The timescales of mineral redox reactions

Redox-reactive minerals can serve as electron donors or acceptors for abiotic reactants or microbial metabolic processes, and hence can play important roles in terrestrial and aquatic environments, particularly if their reaction rates are comparable to those of other biogeochemical processes. Under such circumstances, their reactions can control metal and contaminant bioavailability and change the permeability of soils and sediments. While the thermodynamic driving force for a mineral redox reaction is frequently a good predictor of relative rates of reaction, there are many examples in which kinetic factors limit reaction rate. Understanding the thermodynamic and kinetic aspects of mineral reaction rates, and their sensitivity to environmental conditions such as temperature or pH, is important for anticipating the biogeochemical evolution of natural environments subjected to change. Achieving this goal requires knowledge of the reaction pathway, the timescales of intermediate steps, and the lifetimes of metastable reaction states. Mineral redox reactions proceed through a combination of steps that can include electron and proton transfer, the breaking or formation of bonds, and mineral dissolution or phase transformation. The combination of conventional kinetics approaches, newly-developed ultrafast time-resolved methods and molecular simulation can provide elucidation of such complex reaction pathways. This chapter summarizes key concepts in mineral and interfacial redox reactions with illustrations from the rich geochemistry of iron and ironbearing minerals.

58 GEOSCIENCES↗
NASA NTRS1979

Diffusion and utilization of scientific and technological knowledge within state and local governments

The state-of-the-art is reviewed concerning current knowledge of processes by which technological innovation and scientific information are disseminated among state and local governments. The effectiveness of various mechanisms, strategies, and approaches by which federal agencies have sought to transfer technology to state, regional, and city governments are assessed. It is concluded that the existing relationships between the state and local governments, and the scientific communities are not adequate.

Feller, I.↗
NASA NTRS1983

CO2 on Titan

A sharp stratospheric emission feature at 667/cm in the Voyager infrared spectra of Titan is associated with the nu2 Q branch of CO2. A coupling of photochemical and radiative-transfer theory yields an average mole fraction above the 110 mbar level of (1.5 + 1.5 or - 0.8) x 10 to the -9th, with most of the uncertainty being due to imprecise knowledge of the vertical distribution. CO2 is found to be in a steady state, with its abundance being regulated principally by the 72 K cold trap near the tropopause and secondarily by the rate at which water-bearing meteoritic material enters the top of the atmosphere. An influx of water about 0.4 times that at the top of the terrestrial atmosphere is consistent with a combination of the observed CO2 abundance and a steady-state CO mole fraction of 0.00011; the thoeretical value for CO is close to the value observed by Lutz et al. (1983), although there are large margins for error in both numbers. If steady-state conditions for CO prevail, little information is available regarding the evolution of Titan's atmosphere.

Samuelson, R. E.↗
NASA NTRS1991

NASA/DOD Aerospace Knowledge Diffusion Research Project. Paper 11: The Voice of the User: How US Aerospace Engineers and Scientists View DoD Technical Reports

The project examines how the results of NASA/DOD research diffuse into the aerospace R&D process, and empirically analyzes the implications of the aerospace knowledge diffusion process. Specific issues considered are the roles played by government technical reports, the recognition of the value of scientific and technical information (STI), and the optimization of the STI aerospace transfer system. Information-seeking habits are assessed for the U.S. aerospace community, the general community, the academic sector, and the international community. U.S. aerospace engineers and scientists use 65 percent of working time to communicate STI, and prefer 'internal' STI over 'external' STI. The isolation from 'external' information is found to be detrimental to U.S. aerospace R&D in general.

Pinelli, Thomas E.↗
NASA NTRS1996

Interplanetary and Interstellar Dust Particles: Reentry Heating and Capture in Aerogel

Studies of interplanetary and interstellar dust can provide significant information on the evolution of the solar system or stars, respectively. However, for reliable analysis it is crucial to know how the particles have been modified during reentry (in the case of interplanetary dust particles, or [DP's) and impact into the capture medium. In the case of stratospheric capture, particles will be heated by atmospheric drag. Subsequent capture of the particles will result in heating, ablation, accretion of the capture medium and possible fragmentation. Modeling of these processes is a useful way of assessing their effects on the interpretation of the compositional data for these particles. Previous work on reentry heating has shown that heat diffusion alone cannot adequately account for temperature gradients observed in IDP's. In fact, for any reasonable thermal parameters, calculations show the particles to be nearly isothermal. Here we extend those studies to include phase transitions. These preliminary results are promising and show a significant temperature gradient for a 100 micron (diameter) particle. The actual capture of the particles in silica aerogel is being modeled using a comprehensive shock hydrodynamic code (called CTH). Various options of this code were investigated to attempt to make the most appropriate choice of methods of impact, equations of state, and processes of energy transfer from capture material to particle. The initial calculations with the code used only 'reasonable' estimates for the physical parameters of silica aerogel. Through the literature searches and personal contacts with the knowledgeable scientists, the best possible mechanical and thermal data have been made available for these computations.

Szydlik, Paul P.↗